1. Field of the Invention
This invention relates to methods and apparatus used in the treatment of an orthodontic patient. More particularly, the present invention is directed to methods and apparatus for selecting an orthodontic brace made of one or more components that have been chosen to facilitate achieving a particular objective as determined by the practitioner.
2. Description of the Related Art
Orthodontia is a branch of dentistry that prevents or treats irregular positions of the teeth. Teeth that are not in correct positions may hinder proper chewing of food, and may also tend to develop caries or contribute to gum disease. Furthermore, malpositioned teeth may present an unsightly appearance, especially if located in front or anterior portions of the patient""s oral cavity.
An orthodontic brace is a device used to move teeth to orthodontically correct positions along the dental arch. Typically, the orthodontic practitioner will create a custom orthodontic brace for each patient by selecting components that apply gentle pressure to the teeth in certain directions. Over a period of time, the teeth tend to slowly shift toward desired positions. After an extended period of time, the growth of new bone tissue in areas next to the roots of the teeth will firmly hold the teeth in their new positions.
One type of orthodontic brace that is in widespread use comprises a set of orthodontic appliances along with an archwire. The appliances typically include a number of small, slotted brackets, each of which is mounted on a corresponding tooth along the dental arch. An archwire is received in the slot of each bracket and forms a track to guide the teeth toward desired positions. Usually, a set of appliances and an archwire are provided for both the upper and the lower dental arch of the patient, and treatment of both arches is carried out at the same time.
Today, there are numerous methods for selecting orthodontic appliances and archwires, and the particular selection method used by practitioner is related to the type of orthodontic techniques that are expected to be employed during the course of orthodontic therapy. For example, one popular technique is known as the xe2x80x9cstraight wirexe2x80x9d technique, and involves the use of brackets having slots that are designed to be in a common plane once the teeth have moved to desired, final positions. Although the slots of the brackets are not aligned at the beginning of treatment due to the various malpositions of the teeth, the inherent resilience of the archwire provides a restoring force that tends to move the archwire and hence the slots of the associated brackets into alignment in a common plane.
In the straight wire technique described above, each of the selected brackets has a certain xe2x80x9cprescriptionxe2x80x9d that represents particular characteristics of the bracket. The prescription can include numerous different aspects or features of the bracket, such as the size of the archwire slot, as well as orientation of the slot relative to a base of the bracket that is intended to be mounted on the tooth surface. The prescription describing the orientation of the archwire slot relative to the base may include values for torque, angulation and rotation. In terms of tooth movement, xe2x80x9ctorquexe2x80x9d is often described as tipping movement of the long axis of the tooth in a buccolabial-lingual direction (i.e., in directions toward and away from the patient""s lips or cheeks and the patient""s tongue), xe2x80x9cangulationxe2x80x9d is often described as tipping movement of the long axis of the tooth in mesial and distal directions (i.e., in directions toward and away from the center of the patient""s dental arch) and xe2x80x9crotationxe2x80x9d is often described as rotational movement of the tooth about its long axis.
The prescription of orthodontic brackets often varies from tooth to tooth. For example, many practitioners prefer that the long axes of the lower anterior teeth be as upright as possible, and consequently will prescribe for those teeth a bracket having torque and angulation values that are relatively small. In contrast, the upper central incisor teeth normally have long axes that are slanted. As a result, the practitioner will prescribe upper central brackets having torque and angulation values that are somewhat greater. However, the desired prescription may change from one orthodontist to the next. Moreover, in some instances the prescription is varied from the practitioner""s normal practice in order to accommodate the initial position of a tooth, the location of adjacent teeth or the orientation of opposing teeth for a particular patient.
Another type of orthodontic brace is known as a positioner, and comprises an elastomeric material that is formed in the shape of a tray. The tray has a series of adjoining cavities for receiving the teeth. Each tooth is received in a respective cavity, and the resilient nature of the elastomeric material tends to shift the teeth to desired positions. An example of an orthodontic positioner is described in U.S. Pat. No. 5,055,039.
Orthodontic positioners are often made in the laboratory from a sheet of elastomeric material. One method of making a positioner includes an initial step of making an impression of the patient""s dental arch using an impression material. A model of the patient""s existing dental arch is then made from the cured impression. Next, teeth of the model are cut away and repositioned in wax in desired orientations. The sheet of elastomeric material is then molded over the repositioned model teeth in order to create a custom tray. The elastic material is resilient and has inherent memory, but preferably is sufficiently stiff in order to exert gentle pressure on the teeth when the tray is placed over the patient""s dental arch. The pressure by the tray on the teeth tends to shift the teeth toward desired positions over a period of time.
U.S. Pat. No. 5,975,893 describes a method for incrementally moving teeth using a series of polymeric trays in successive order. The trays are designed by a computer to provide a plurality of different, intermediate tooth arrangements as well as a final tooth arrangement. Each tray is sufficiently resilient to provide corrective forces in order to move the teeth in relatively small increments and toward the desired, final tooth arrangement.
In the past, orthodontic practitioners have often selected prescriptions for braces by their first-hand knowledge of past treatment results with other patients and by reviewing results reported in the literature. However, some patients present unique problems, and reference to techniques that have been satisfactorily used in the past may not be suitable for certain patient""s in the future. For example, a force module may be desired in a particular instance to assist in moving the teeth, and the force module may affect the final positions of the teeth to such a degree that the prescription should be changed.
Moreover, the problem of selecting an orthodontic prescription is aggravated by the nature of orthodontic treatment because the results of treatment may not be apparent for some time. Tooth movement is carried out slowly during orthodontic therapy, in order to reduce the amount of pain experienced by the patient and also to give sufficient time for the bone to grow and fix each tooth in place in its new position. As a result, practitioners prefer to make certain that the prescription of the brace that is initially selected is satisfactory for moving the teeth to desired, final orientations.
In addition, it is sometimes difficult for practitioners to predict the effects of tooth movements when a change in the prescription of the brace is made. The problem of predicting tooth movement is compounded by the fact that the roots of the teeth are not visible in ordinary view. Furthermore, spatial cognition of tooth movement in three dimensions is difficult, especially when such tooth movement may be influenced by the positions of adjacent teeth along the dental arch.
As can be appreciated, it would be desirable to provide a system for facilitating the selection of a custom orthodontic brace, and in particular to provide a system for facilitating the selection of a prescription for a custom orthodontic brace. Preferably, such a system would be easy to use and would facilitate the understanding of long-term effects of the particular brace selected. Moreover, such a system should be adaptable for use with any type of brace, including positioners, a series of custom trays, systems that include brackets and archwires as well as other types of braces.
The present invention is directed toward methods and apparatus that facilitate the selection of a custom orthodontic brace. In accordance with one aspect of the invention, images of the teeth are displayed in orientations representing final orientations at the conclusion of treatment with a first brace, as well as in orientations representing final orientations at the conclusion of treatment with a second brace. The images representative of results obtained from both the first brace and the second brace are simultaneously displayed, preferably in contrasting images, so that the relative effects of the two braces on the resulting positions of the teeth can be easily observed. In this manner, the practitioner can better understand the cause and effect relationship between the selected brace and the final or finish positions of the corresponding teeth.
In accordance with another aspect of the invention, images of teeth are displayed in orientations during a stage of orthodontic treatment that precedes a final stage. The stage may be an initial stage or an intermediate stage. Images of the teeth are also displayed in orientations representing final orientations at the conclusion of treatment with a certain brace. The images in the finished position and in the preceding stage position are simultaneously displayed, also preferably in contrasting images, so that the effect of the certain brace on the teeth can be readily observed.
In more detail, the present invention is directed in one aspect to a method of selecting a custom orthodontic brace. The method comprises:
providing a set of data representative of a number of teeth of a dental arch;
selecting a first orthodontic brace for at least some of the teeth in the dental arch, wherein the first brace has a certain prescription;
determining first positions of the teeth as they might appear when the first brace is mounted on corresponding teeth;
selecting a second orthodontic brace for at least some of the same teeth in the dental arch, wherein the second brace has a prescription that is different than the prescription of the first brace;
determining second positions of the teeth as they might appear when the second brace is mounted on corresponding teeth; and
simultaneously displaying an image of at least one tooth when in the first position and when in the second position, wherein at least part of the images are overlaid, and wherein at least a portion of any difference in the orientations of the displayed tooth images between the first position and the second position appears in contrast so that the relative effect of the first brace and the second brace can be observed.
Another embodiment of the present invention is also directed to a method of selecting a prescription for an orthodontic brace. In this embodiment, the method comprises:
providing a set of data representative of a number of teeth of a dental arch;
selecting a first orthodontic brace for at least some of the teeth in the dental arch, wherein the first brace includes a first set of appliances comprising an archwire and a number of brackets, and wherein each appliance of the first set has a certain prescription;
determining first positions of the teeth as they might appear when the first brace is mounted on corresponding teeth;
selecting a second orthodontic brace for at least some of the teeth in the dental arch, wherein the second brace includes a second set of appliances comprising an archwire and a number of brackets, wherein each appliance of the second set has a certain prescription, and wherein at least one appliance of the second set has a prescription that is different than the prescription of one of the appliances of the first set;
determining second positions of the teeth as they might appear when the second brace is mounted on corresponding teeth; and
simultaneously displaying an image of at least one tooth when in the first position and when in the second position, wherein at least part of the images are superimposed with respect to each other, and wherein at least a portion of any difference in the orientations of the displayed images between the first position and the second position appears in contrast so that the relative effect of the first brace and the second brace can be observed.
Another aspect of the present invention is also directed to a method of selecting a custom orthodontic brace. This method comprises:
providing a set of data representative of a number of teeth of a dental arch;
displaying at least one tooth of the dental arch as a first image in an orientation as it appears during one stage of orthodontic treatment that precedes a final stage of orthodontic treatment;
selecting a certain group of orthodontic appliances for the dental arch, wherein the certain group of appliances includes an archwire having a certain prescription and a number of brackets, each of the brackets of the certain group corresponding to one of the teeth and having a certain prescription;
determining finish positions of the teeth as they might appear when the brackets of the certain group are mounted on corresponding teeth, the archwire of the certain group is connected to the brackets of the certain group and the teeth have moved in response to forces exerted on the brackets of the certain group; and
displaying at least one tooth in its determined finish position as an image, wherein at least a portion of any difference in the orientations of the teeth in the displayed finish positions appears in an image that contrasts with the image of the teeth in the displayed preceding stage positions so that the effect of the certain group of appliances can be observed.
An additional aspect of the present invention is also directed to a method of selecting a custom orthodontic brace. This method comprises:
providing a set of data representative of a number of teeth of a dental arch;
displaying at least one tooth of the dental arch as a first image in an orientation as it appears during a first stage of orthodontic treatment;
selecting a brace for the dental arch, wherein the brace has a certain prescription;
determining second positions of the teeth as they might appear when the brace is mounted in the oral cavity and the teeth have moved in response to forces exerted by the brace; and
displaying at least one tooth in its second position as an image, wherein any difference in the orientations of the teeth in the displayed second positions appears as an image that contrasts with the image of the teeth in the displaced first positions so that the effect of the brace can be observed.
Yet another aspect of the present invention is directed toward a method of manipulating data of a dental patient""s tooth. This method comprises:
obtaining a first set of data representing the shape of at least a portion of a patient""s tooth;
providing a second set of data that represents the shape of at least a portion of a model tooth that is of the same type of tooth as the tooth represented by the first set of data;
manipulating at least some of the data of at least one of the first set of data and the second set of data so that the scale of the patient""s tooth and the scale of the model tooth are substantially the same; and
combining at least some data of the first set and of the second set in order to obtain a third set of data that represents at least part of the model tooth and at least part of the patient""s tooth.
The present invention is also directed in another aspect to a computer readable medium that tangibly embodies a program executable for performing selection of a prescription for an orthodontic brace. The computer readable medium comprises a set of data representative of a number of teeth of the dental arch, and first means for displaying images of at least some of the teeth in first positions as they might appear when a first brace is mounted on the teeth. The computer readable medium also comprises second means for displaying images of at least some of the teeth in second positions as they might appear when a second brace is mounted on the teeth. The second means includes means for simultaneously displaying at least some of the images of the same teeth in the second positions and the first positions. At least part of the images of the displayed teeth in the first position and in the second position are superimposed.
The present invention is also directed in another aspect to a computer readable medium that tangibly embodies a program executable for performing selection of a prescription for an orthodontic brace. In this aspect, the computer readable medium comprises a set of data representative of a number of teeth of the dental arch, and first means for displaying images of at least some of the teeth in positions as they might appear during a first stage of orthodontic treatment. The computer readable medium also comprises second means for displaying images of at least some of the teeth in second positions as they might appear when a certain group of orthodontic appliances is mounted on the teeth. The second means includes means for simultaneously displaying at least some of the same teeth in the first stage positions and in the second stage positions. At least part of the images of the displayed teeth in the first stage positions and in the second stage positions are superimposed.
Additional features and advantages of the invention are set out below in the paragraphs that follow and are described with reference to the accompanying drawings.